Starting device for free piston internal-combustion operated compressors or gas generators



R. J. WELSH Sept. 23, 1952 2,611,233 STARTING DEVICE FOR FREE PISTONINTERNAL-COMBUSTION OPERATED COMPRESSORS 0R GAS GENERATORS 3Sheets-Sheet 1 Filed July 18, 1947 Sept. 23, 1952 J WELSH 2,611,233

STARTING DEVICE FOR FREE PISTON INTERNAL-COMBUSTION OPERATED COMPRESSORS0R GAS GENERATORS Filed July 18, 1947 3 Sheets-Sheet 2 Sept. 23, 1952 R.J. WELSH 2,611,233

STARTING DEVICE FOR FREE PISTON INTERNAL-COMBUSTION QPERATED COMPRESSORSQR GAS GENERATORS Filed July 18, 1947 3 Sheets-Sheet 3 R r 1 0 l G aim/A,

Fatenteri Sept. 23, 1952 UNITED STATE PAT oFFi cE STARTING .DEVICE FORT-ERNALI-..COMBUSTION OPERATED NE-1 PRESSOKS ,OR..;.G'AS GENERATORS Robert a;

to The.

me welshiR hyiEn a d gn English Electric "Comp any 1 Limited,

London,- E ng'land', a British company:

Annlicatiqnziu x L8 1947, i LN 1 7 2 InGreatBriiain. May 24-, 19 45 (CLGil-14)- 11 Claims.-

isnv nt on s. mqii fication. of hes venr tion describedjn Patent .Nos2,43%,877 (applica tion No. 559,976); fi1ed October 23, 1944 andjrelatesto, a starting device for airee piStQn. inter; nal combustionoperatedeompressor i.,e. anengine wherein a compressor pistonsisdirectly connected to, or combined with, an internal combustion engine.piston. ancl wherein the motion.

o i v nis oh..a sembly i n co r inedlb c s pi ing through connectingrods and cranks to rotating members. There. areusuallytwo opposed enginepistons reciprocable towards andlaway from each other oneoylinder.Theengiine is u ua ly one wh b e tesen, a two-stroke-copressiOn-igni-tion cyjcle some; orall of. the, air from thefcompress'orserving to scavengeand harge t e. n ne. cylinder...

An en ine ofth'is kind. may. befused. as a gas-s n a or. to uepl r t e ic of ap a at s.

such as a gas. turbine. wh h. ay have as its. wo n fl i iei h r oz. sollyair ominsfi from. e qmnre s rmt i). sole y hsfexha st.

f om th e in c linde co pr sing; the. pr ucts: offjthecombustion the.engine cylinder mixem h. th cav ns nsg s p icd to h ensi 'esby he mpresor). or (iii) am xt e o the. en i e. e ha st h. airs omi s d ect fromthe mpr n hesec ndofthese hree a e natives is most usual.

The invention. employs gaspressure from, a,

sou otter. exam le. compr sse i o a t: me; th en n h s. saseh reinaterie r dito s ai rb na dmi ted eith r. to an u i ar s r ine y nder or tc inde erv s m the un i n. dur nsnqrme per tio .o the.

en ne A r e pis on ty ecompresso Q sas.

enerat as .defin deb re. has u ually. in. addi 'i ito he. nt rna cmbustion d ompre sor. ylinders, a separate. buf ee y nder. orlcy in ers.

in wh ch, reciprocates so e par f e. r e piston assembly forcompressingeir during the expansion stroke ointhe engine, the pressureof whichair seryesto, return or to assistin the return of the 7 treepiston assembly. and the cornpression of afresh chargein theuinternfll.combustion cylinder in readiness. forlthenext expansion. t 9k and e, enine. may ns a ted by. upp ying comp ess dja r rom. a sou f. ome parively. un estr cted.capa ity. to this. .buf er.

yl n r 0 hs.. m t s r .fiy inioler.v It? s necessary that this supply ofair-or indeed the application'ofair many-other way-tor starting theengine-should= not interferewi-th subsequent normaloperation;-The'starting air will escape from s the cylinder inthe: usual way at the:end of a full stroke through .a port uncovered rbythe pistonrwhen; nearits. inner dead,.-centre position.

compressed air toga cyl inderof the engine in? a number of automaticallyrepeated, impulses" whereby-the free. piston assembly isreciprocated.until the engine fires regularly, when-the supply 01 compressedflir iscut ofiand the normal opera.- tion of the engine. begins.

The free piston assembly maybe set at or near.

to its outer dead centrevp osition inreadinessior starting, An operatingmember such asa cam which is controlledg'by the free piston assembly" inaccordance with its position "relative to the engine cylinders is soarranged as to opena ve lvein the supply lineof compressed air to the.

respective cylinder .oi the engine wheneverthe piston s e l a es, a. an-" euse it outer portion of its stroke.

Whe artinsthe ngine, i se spe se through the first stroke fromthe, said.position.

T einyent qn emrrisesmeansionadmitting at, or near .to the'outer.deaclicentre; under the influence of compressed ,air admitted directly;

into the cushion cylinden. The said; cam "or the like then opensthe-automatic'valve arid-admits; an impulse of; compressed=air*to-;the"inward1y moving piston assembly-which; consequently -is,

clrivenvigorously towards its inner dead-centre" position.

The automatic valve ,is openedag ainby'the said cam when the pistonsrebound, from theirv inner dead centre position under-theaction nf theair Which is compressedin-the combustion ylinder under, h pressure ofi'h n e na combustion if the engine fires-the compressed air. havin m t yesc ed. r m e cush nw nd x. at. the inner ,end' o ii s s roke so hat: nahnormalinw rd fo c oppos sa d eb undr A nswinwa id impu s yei n o thenee piston assembly when reaching again the outer. ortionof its str0ke,. but, this time at-a point more remote from "theouter deadcentre'posiion,. hi pu se dr sthe ree pis onassem" m back w rdstsj..inner. dead" ce r sition the case of the pawl and ratchet device(Figs. 3 to 8) the compressed air supply being shut, or by virtue of theposition of cam 33 in the embodiment of Fig. 2 which is related to theposition of the generator pistons. Once the first impulse has beeneffected both embodiments continue to give a series of impulses untilthe generator is firing correctly, after which both embodiments rely onthe air pressure to close their respective valves 55 or 38.

In the present application, too, air is admitted in a number of impulsesbut the duration of these impulses is timed in a different manner, 1. e.by means of the rotational oscillation of the starting cam I (Fig. 4)oscillating in accordance with the reciprocating movement of the freepiston units, in conjunction with a master starting valve I (Fig. 2).When starting air is admitted to the starting device from the masterstarting valve I0 the air tends to keep valve 3 (Fig. 4) closed but theair which has got past valve 3 starts the generator piston units movingwhich in turn oscillate the starting cam I. The cam I thus suddenlyopens the valve 3 allowing a sudden impulse to strike the generatorpiston units which starts the units reciprocating. This movement of thepiston unit continues to cause cam to open valve 3 periodically thuspassing a series of air pressure impulses, one per stroke, to the freepistons until the generator is running. The master starting valve I0then shuts off the starting air supply to the engine, the cam device Inot having any control over the air supply from the pressure source.

A different aspect of the problems involving the starting of free pistonengines is dealt with in Patent No. 2,434,778 (application No. 546,360)filed July 24, 1944, which is for the cyclic control, i. e. arrangingthat the gas generators come into action when required in a cyclic orderso that each will do a fair share of work over a long period.

In order to be better understood and readily carried into effect, theinvention will be described by way of example with reference to thedrawings, of which:

Fig. 1 shows a general arrangement of a free piston internal combustionoperated gas generator incorporating the starting device according tothe invention,

Fig. 2 shows a master starting valve connected with the generalarrangement of Fig. 1, forming, in fact, part of it, and shown in aseparate figure only for clarity to allow of a bigger scale for theFigure 2,

Fig. 3 shows a detail of Fig. l on an enlarged scale, and

Fig. 4 is an elevation, partly in section, on a larger scale, of anembodiment of the starting device according to the invention, asdiagrammatically indicated on Fig. 1.

Referring first to Fig. 1, the free piston internal combustion operatedgas generator comprises, as usual, a common combustion cylinder IOI, twocompressor cylinders I02 in alignment with said combustion cylinder oneither end of it, and two cushion cylinders I03 in alignment with and onthe outer ends of said compressor cylinders. Two free piston assemblies,each consisting of a combustion engine piston I04, a compressor pistonI05 and a cushion cylinder piston I05 are adapted to reciprocatesymmetrically in the said cylinders, synchronization between them beingeffected for example by the usual linkage system I01, I08, I01.

Air is supplied through the inlet manifolds I4 and spring-loaded suctionvalves I2 (one only of which is shown per side) into the compressorcylinders I02 the inner sides'of which are vented to the atmosphere byports I02a. Compressed air is sup lied from the compressor cylinders I02through spring loaded delivery valves I3 (one only of which is shown perside) and transfer pipes I5 to the chamber |2| surrounding thecombustion cylinder IOI, into which it is discharged as soon as theports |0|a are uncovered by the right hand side piston I04.

When the pistons are in or near their inner dead centres, fuel oil isinjected into the combustion cylinder IN by a conventional fuel pump 0through pipes I1, distributor I8, pipes l9 and injectors I09. When thepistons, operating on a two stroke compression ignition cycle, havemoved outward far enough to uncover the exhaust ports IOIb, the exhaustgases and compressed air scavenging the cylinder 0| via the ports I0|aand |0|b are discharged through pipe I6 to a gas turbine (not shown) asthe motive gases for such prime mover.

The fuel pump 0 is controlled by the usual rack HM and operated by a camIII which is oscillated by a lever 20 which is connected by the link 2|with a component such as I01 of the synchronizing mechanism for the freepiston assemblies.

Another cam |,'the purpose of which will be described later inconnection with the starting mechanism according to the invention, isalso oscillated by the said synchronizing mechanism, and so is a lever|08a operating, through a link 28, the running indicator 31 shown on thebottom of Fig. l and, on an enlarged scale, separately in Fig. 3. Therunning indicator (Fig. 3) is a hydraulic device comprising piston valve36 reciprocated by the link 28 in a transverse cylinder in the body 31.In one extreme position this valve 36 connects one of two longitudinalcylinders in the same body to fluid pressure supply pipe 38 through acomparatively restricted orifice 31b and the other of said cylinders toexhaust through a similar orifice 37a; in the other extreme position thevalve 36 reverses these connections while during its movement from oneposition to the other the valve temporarily connects both cylinders toexhaust. In each cylinder is one of a pair of double pistons 39 and 40which, under fluid pressure through orifices 37a and 31b, can moveoutwards against a very light biasing force provided by springs 4|.These pistons form valves which serve together to connect the pipe 33 toexhaust 310 only when applied pressure has moved both piston out; wheneither is held in by the biasing force of spring 4|, the pipe 33 isconnected to the fluid pressure pipe 42, which is supplied by any knownsource of pressure such as any suitable oil pump, not shown in thedrawing for simplicity. When the engine is at rest the control valve 36can only be in a position in which at least one of the said cylinders ofthe running indicator" is connected to exhaust, and so the pipe 33 willbe connected to pressure. When the engine is running and the controlvalve 36 is reciprocating the said cylinders are connected alternatelyto pressure and to exhaust but they are not connected to the exhaustlong enough through the restricted orifices 37a and 31b for the lightbiasing force of springs 4| to impart any appreciable inward movement toeither piston; accordingly both pistons remain out and the pipe 33 remaiam nesto move outwards to bear on :a shoulder Eaton the inner side ofthe .right hand compressor piston (which is linked to thezlefthand comepressor piston 5 by the linkage 7,, 6, i indicated in dotted lines inFig. 2') so as toadrive the .free pistons to their outer dead centre-position. When the free pistons approach or reach their outer deadcentre position a cam 43 actuated by them through link 29 andthe-leverconnected by the link 2| to the synchronising linkage, .is rocked aboutthe fixed pivot 44 to engage a .roller on the projecting end of thepiston .rodoi the end of stroke indicator, forcingthe triple piston 3 tinwards to thew position shown and thereby connecting the fluid pressurefrom pipe 33 by way of pipe it to a rear part of: the. .barring relay,behind the piston 3!, which is shown as of greater area than the frontpiston-36 so that the force .from the rear will overcome that from thefront. The latter relay isthus moved back .to its normal position (asshown) to dis connect pipe Ztand the barring cylinder .26 from the pipe33 and to connect them to exhaust, whereby the barring piston 24 .iswithdrawn by the action of a biasing force such. as that of a spring t?and the relief valves 21 in the buffer cylinders 3 can recluse. Thebarring piston 24, when completely withdrawn, re-establishes aconnection from the pipe 33 through the end of stroke indicator cylinder35, pipe 46, and ports uncovered and put into communication by thereduced portion 24a of the piston rod of the barring piston 24 to pipe38 and .a port in a starting relay 49 hereinafter described withreference to Fig. '3. When the barring piston and co-operating partshave gone through the operations described the whole equipment isthenreset and ready for restarting, there'setting having taken placeautomatically. inirnmediate response to the stopping of the engine. h h

A barring cylinder 25 is arranged, preferably within the casing l2l thatsurrounds the combustion cylinder llll, so that the free end or the rodof piston 24 fitting said barring cylinder will alsobe "describedlater'moreinzdetail; zilalvt'i i0 is connected with acomparativelyunlimited supply of compressed air. through pipe 6 I.

Referring now particularly to'Fig. 3 the *running indicator 31 operatesas follows-e V The link 28 "which, as previously stated operatestherunning .indicator,..is coupled tothe piston valve 36 which istherefore oscillated when the free piston compressor is running. Thelength ofthe valve 316 .issuch that whenithe compressor is at rest oneor other of 'ther-ports 31a or 31b'is open to exhaust pastithe :outer.edgesoj: the valve andthe remaining port (3111; or 31b.) .isopened topressure from the pipe .38 by-one of'the inside edgesLof the.lvalive..*= :[n-iav rest position with the valve 36 in the position.

- shown, fluid pressure from ithesupply pipe 42 is adapted to bear onthe shoulder 3522' of "one of the compressor pistons I05). A'springiitends to withdraw the said piston 24. intoits cylinder 25.

Spring loaded ventvalvesttliare arranged in each of the cushioncylinders E63, which are moreover vented by ports] 103a whenever'fthepistons .l 66 approach their inner dead centre .1 0- sitions, The valves2? canbe opened against their spring bias] under "fluid pressure comingfrom pipes 26 and acting on pistons integral with said valves. 1 i

Compressed air can be'supplied to. the cushion cylinders I03 throughspring .loadedfautomaticf non-return valves 22irom pipes'BmYSh'connected with the automatic starting regulator valve-4 which will bedescribed more indetailwith reference to Fig. 4 and which is connectedby-pipe 5. to the master startingvalve -l-.0-".(Fig;i2'). which willpass through the pipe 38, enterthe recess the valve 36, pass through theopen portfflb andimovje thepiston it. to the left1againsti1tsl. Weakspring ll. L 'j' The port 37a is closed to pressure from pipej3'8, bythe valve 36 but is .open to exhaust past the upperedge of the saidvalve and 'will tliere'fore be moved to the right by its'spring ll."Pres? sure fluid can" also pass byway of thebranch pipe 12a,.throughthe recess in piston 39, the oblique port 'B'Id-and'the recess'in pistonWfto the pipe 33. It will be clear'fromFig. 3 that if the free pistonassemblies were in a rest position whereby the valve 36 was movedupwards to open port B'ia to press'urefrcm pipe '38 and open port 31b,to exhaust past its lowest edge, the pea siticns of pistons 39 and;ifiwould be,.,revers.ed.

" Pressure'irom pipe 42 could still, however; reach pipe 33 because,piston 40 would be .inovedfto the right by its springj -iiwhereby branchpipe 42b would communicate with pipe 33 through, the recess in pistonit. andthe oblique port 3111' would be closed by the left hand end'ofthe said piston. Piston 39 would be in the left'handjposition and thepipe 52a would be shut off. 7

As soon} however, as the free pistonassembly is reciprocating, thepiston valve 36 is oscillated through its link connection 28 and leverjtfiaisoj that the ports 37a and 31b are alternatelyopened to pressurefrom pipe 3.8. and to ex'haustpastthe outer edges. of the valve.Suficient jfluidPre'ssure is passed through pipe 3.8 round .the'reces'sof .valve 36 (and the ports 31a and. 31b to .feic'e both pistons 35'and36 to the leit againstjtheir weak springs iii. The ports 31a and 31b areof a .estricted cross section and .do not anew escape of fluid toexhaust to take place'quiclily I enough is eflect the building- 11p ofpressure n; side the rcylinders for'the pistons 39 .a'ndfdili From Fig.3 is will be seen that this position of the running indicator in whichboth pistons. 39'and ill are over .tothe left, vpipe .33 is out ofi.from both branch pipes Ma and Mb and hence from pressure from pipe 42and is vented to exhaust at 31c past the recessed portions of bothpistons, 39, 46 and the oblique canal; 371i in'the body of the casing31. v Thus pipe 133 is under pressure when-the free piston compressorisstationary, and .is :opened to exhaust when the compressor isrun'ning:s F Returning now to Fig. l, the barring cylinder 255is. connected withthe barring relay .32' by. pipe 2'6'which, 'as mentioned :above,supplies 'fluid pressure also to the pistons of the ventivalves 21 The:barring" relaycomprises two .lc ylinders 7 cylinderis connected throughpipe '33 with the .running indicator 31 and through the latter with asupply of pressure fluid 42. The inner port of the small cylinder of thebarring relay 32 is connected with the aforementioned pipe 26. The outerend of the large cylinder is connected through pipe 46 with the bore inwhich the rod of piston 24 is adapted to move. In the inner position ofsaid piston 24 a recess 24a in the piston rod opens a passage for thefluid from pipe 46 to pipe 48 but in the outer position of piston 24said passage is blocked by the piston rod. The inner end of the largecylinder of relay 32 communicates with the inner end of the smallcylinder of said relay and is open to exhaust at E.

'- Barring operation Fluid pressure from pipe 42 is supplied through therunning indicator 31 (in the position as shown in Figs. 1 and 3) andpipe 33 to the outer end of the small cylinder of the barring relay 32.A branch of pipe 33 is connected with the. end of stroke indicator" 35,and the fluid pressure from pipe 33 pushes the tripartite piston 34thereof to the right where it connects pipe 46 to exhaust at E.

As the outer end of the large cylinder of the barring relay 32 isconnected with pipe 46, the fluid pressure on the outer end of the smallpiston 30 can push the pistons 30, 3I to the right, thereby uncoveringthe port of pipe 26, and. admit fluid pressure through said pipe to thepistons of the vent valves 21, opening them, and to the barring cylinderthe piston 24 of which will then be moved to the right, against the biasof spring 41, and push the free piston assemblies I04, I05, I06, near totheir outer dead centre position, the air from the cushion cylinders I03escaping through the vent valves 21.

The outward movement of the free piston assembly is transmitted by thelink 29 to the cam 43 which pushes the tripartite piston 34 back to theleft hand position as shown where it connects pipe 46 to the fluidpressure from pipe 33 which acts now on the outer side of the largepiston 3| of the barring relay 32 and pushesit back to its left handposition as shown, overriding the pressure acting on the small piston30. Any fluid contained betweenthe pistons and 3I is drained at E, andas soon as piston 30 has cleared the port of pipe 26, the pressure inthat pipe also escapes through E. Consequently the vent valves 21 closeunder the spring bias,'and the barring piston 24 is withdrawn tothe leftinto its cylinder 25 by its spring 41. v

In this retracted position of the barring piston 24, communication isestablished through the recess 24a, as stated above, between pipe 46 andthe pipe leading to the starting relay 49 shown in Fig. 2.

Starting relay with a pipe 15 adapted to apply fluid pressure underremote control. The central portion of the cylinder 48, i. e. the conecorresponding to 8 the wide recess 50d of the piston. is connected withthe aforesaid pipe 48.

The portion of cylinder 49 which is cut oil! from pipe 48 by the piston50 in its right hand position as shown is connected by a pipe 54containing a non-return valve 66 and a by-pass 61 containing anadjustable leak-off 68 with the servo-motor cylinder 55 containing twopistons 56, 51 spaced apart by a spring 58. Piston 51 is adapted to bearon the stem of the master valve I 0 which is normally kept in its closedposition by its own weight and by the air pressure coming from thesource of compressed air via pipe 6| acting-on its upper surface. Theunderside of said master valve I0 is connected by pipe 5 with the casing-4 of automatic starting regulator valve which is shown in outline inFig. 1 and in section'on a larger scale in Fig. 4.

Starting regulator Referring now particularly to the last mentionedfigure, a cam I is arranged on a shaft A which performs a rotationaloscillation inaccordance with the reciprocating movement of the freepiston assemblies I03, I04, I05 by being connected, for example, in thelink mechanism I01, I08, I01 serving to synchronize the movements of twoopposed free piston assemblies. Cam I engages a roller 2 at the end oflever 2a which is pivoted on a lug of the-valve casing 4 and carries anadjustable screw 212 that engages the end of the spindle of a valve 3the seat of which is arranged in the casing 4. This casing is connected,as stated, with the source of compressed air supply by a pipe 5 in whichthere is the master valve I0, an automatic embodiment of which has beendescribed with reference to Fig. 2, and by pipes 6a, 6b, with thenon-return valves 22 (Fig. 1) leading into the cushion cylinders I03 ofthe free piston compressor.

In the position as shown in Fig. 4, the valve 3 is in its closedposition, which it assumes in operation under the excess pressure of thecompressed air acting on its under side unless it is depressed by thelever 2a operated by cam I as will be described later more in detail.

When in readiness for operation the valve 3 is, however, in its openposition into which it drops under its own weight'at the end of theforegoing starting operation.

The connection of cam I and shaft'A may be adjustable, for example, bymeans of slots Ia in the disc of cam I which are engaged by clampingscrews lb connected with a flange (not shown) of shaft A.

The movement of valve 3 is limited by a stop 1 so as to keep theundersurface of the valve exposed to the onrush of the -compressed airwhen the master valve I0 is opened.

Starting operation The starting operation is as follows:

The free piston assemblies have been barred" at, or preferably slightlyinwards of, their outer dead centre position as described. In thisposition of the free piston assemblies, cam I is in the position asshown in Fig. 4. If now the master valve I0 is opened, as will bedescribed later more in detail with reference to Fig. 2, air from pipe 5is admitted to the cushion cylinders I03 past the open-valve 3 which,however, is then lifted by the onrush of air and subsequently heldagainst its seat in the casing 4 by the excess air pressure acting onits underside.

Under the action of the'compressed air that got into-thecushioncylinders, H13, past valve 3 beforeit closed, the :free pistonassemblies I94, I05, I06 are, moved inwards ,from their position neartheir outer dead centres, This movement istransmitted through axis A tocam I which depresses the roller- 2 of lever 2a which, in turn,momentarilydepresses and opens valve 3.

Compressed air is thus admitted from the supply pipe 5 through valve 3,pipes 6a, 6b, and thenon-return valves22 to the, cushion cylinders'Hid-and the free piston assemblies are ac celerated inwards.

Fuel may be injected into the combustion cylinder, [i already at thisstage and the energy of the explosion, although not yet 'sufiicientj toestablish regular operation, may assist in re.- turning the free piston"assemblies. towards their outer, dead centre position; On this returnmovement of the free piston assemblies, thecam l3doespnot move asfar outas shown in Figs-4,

but farenough to depress the roller 2 with the opposite side ofrthe camtoe and thus to open thevalve 3 momentarily "and to admit anotherimpulse of compressed aircto the cushion cylinders l 03' which furtheraccelerates the vfree pistonassemblies; inwards. This is repeated untilthe engine is firing regularly.

- Referring now-particularly to Fig.3, it will bedescribed how themaster valve. H) of the compressed air supply canbe opened for, and

kept open during, thestarting operation, and be 1closed again as soon;as the engine is firing regui ly s If fluid pressure is applied, .say byremote controlptothe right, of ,pistonill through. pipe 15,

the piston. valve 58 ismoved to the left and pipe 54 will thus be. putin communication with the fluid'pressure supply pipe; 43. As has beenpreviously' explainedunder the heading Barring- Operation, when the;free piston assemblies have been barred out to a position ready forstarting and the running indicator is at rest, that pressure fluid frompipe 42- can pass through the running indicator to line. -33, throughthe end of stroke, relay 35 in the left hand position of piston-34topipe 46, and past therecess 24aof the barring piston rod to pipe 48;Therefore, with the starting relay piston 50: in its left handposition,pressure fluid flows from pipe 48 (Fig. 2) pastthe wide recess 50d oipiston 58, through pipe 54 and non-return valve 66 to the underside ofthe servo-motor piston 56. Accordingly, this piston rises,, compressesspring 58 until piston d'lpvercomes the airpressure acting on the top ofthe master startingvalve l0, and throws it open, whereby the startingoperations as described hereabove are initiated. I

When the free piston assemblies are reciprocating, pressure is removedby the running indicator from the pipe 33. The drop of pressure in thispipe would: be transmitted to the servomotor cylinder via pipe A6,recess 24a, pipe 43. relay cylinder 49 and recess 513d of piston valve50, but the non-return valve 66 closes and the pressure in theservo-motor cylinder 55 can escape but gradually through icy-pass 51 andthe leak-off 6,3 to exhaust at E" so that the master valve l0 cutsofitheair supply with suiii'cient delay to allow the repeated applicationof: starting air as described. V

"Recess 50b andboreiilc in piston 50 drain ofi to exhaust at E" anypressure fluid which might have leakedinto the .righthand end ofcylinder 49 from pipe 48 and thus prevents any unintentional starting.

Any ordinary handor remote-control master air valve It may be usedinstead of the. auto matic device as shown in Fig. 2.

'What I, claim as my invention and desire .to secureby Letters Patentis: p I 1. In a free piston internal combustion operated gas generatorplant comprising a-gas gencrater-having an engine cylinder, atleast onecompressor cylinder, atleast one buffer cylinder and at least one freepiston assembly consisting of'an'engine piston, a compressor piston anda buffer: piston freely reciprocating in the said cylindersanunrestricted source of compressed air, a pneumatic connection fromsaid source to the said 'bufier cylindena hydraulically operated masterstartingrair valve in said pneumatic connection, opening againsttheairpressure of said source, a source or: hydraulic pressureya hydraulicbarring relay, an'end of stroke indicator, a running indicator operablyconneQted to the said free piston assembly, hydraulic con.- nectionsfrom the said'source of hydraulicpressure through the said runningindicator to the saidbarring relay: and end of stroke indicator; thesaid running indicator connecting the said 1 barring relay and the saidend of stroke indicator to the said source of hydraulic pressure whenthe gas generator-isat a standstill and cutting them on when it isrunning, a spring biased hydraulically operated vent valve'in the saidbuifer cylinder, a spring biased hydraulic barring servomotor,hydraulicconriections' from the said barring relay and the'said end ofstroke indicator to the said vent valve and barring servomotor, the saidend of stroke indicator and the said barring :relayi admitting hydraulicpressure tofthe said vent valve and barring servomotor when the saidfree piston assembly is-in'a position remote from the starting positionwhereby the said Vent valve is opened an'd'the said free'pistonassemblyis barred into its startingposition, 'andjc-utting off said'ventvalve and barring servomotor from hydraulic pressure when the said {freepiston assembly is in the starting position, the said vent valve, beingthen closed and the said barring servomotor withdrawn by theirrespective spring bias, a hydrauli'cconnection of the said barring relayand. end of stroke indicator to the said hydraulically operated masterstarting valve, and a valve in this" lastt mentioned hydraulicconnection controlled by the said barring servomotorsoasto beopenedinthe retracted position thereof and closed during the barringoperaf tion: a starting relay, a starting device comprisin incombinations. starting air regulator valve, anon-returnvalve, both saidvalves arranged in succession in the, said pneumatic connectionbetweenthe saidmaster starting air valve and the said cushion cylinder, and astarting cam oper-' ably connected. to the said free piston assemblyandopeningsaid starting, air regulator valve in synchronism with thereciprocating movement of the said free piston assembly whereby compressed 'airis admitted, through the saidnomre turn. valve to. thesaidbuiier cylinderin a-nurnber of. pulseswhile themasterstartingvalveiskept and-fro in the said cylinder, the outer end of the narrowportion of the said stepped cylinder being connected with the saidrunning indicator, and a port in the said narrow portion being connectedwith the said barring cylinder and the said fluid pressure operatedvent-valve, the space between the narrow and wide portion of the saidstepped cylinder being open to exhaust and the end of said wide portionbeing in pipe connection with the said end of stroke indicator.

3. A starting device as claimed in claim 1 comprising a recessed pistonrod of the said barring servomotor, a pipe connection between the outerend of the large cylinder of the said barring relay and a portcontrolled by said recessed piston rod, a pipe connection between thesaid master starting valve servo-motor and another port controlled bythe said recessed piston rod to admit communication between the saidbarring relay and the said servo-motor only when the said piston isretracted out of the range of the stroke of the free piston assembly.

4. A starting device according to claim 1 in which the said startinregulator valve comprises an air valve casing, a valve arranged in saidcasing and adapted to be closed by compressed air admitted to theupstream side of said air valve casing by the said master starting valveand to be opened by the said cam operably connected to the free pistonassembly whereby compressed air can pass said valve and enter the saidcylinder of the compressor or gas generator each time the free pistonassembly reaches a point near the end of its stroke.

5. A starting device according. to claim 1 wherein, as a means forinitially moving the free piston assembly from its starting position,the said starting cam has a profile holding the said starting regulatorvalve in an open rest position exposed to the air stream from the saidmaster starting valve when the latter is opened, and permitting the saidstarting'regulator valve to be closed by the said air stream when thefree piston assembly is moved from its starting position.

6. A starting device as claimed in claim 1, in which the said end ofstroke indicator comprises a ported cylinder, a tripartite pistonadapted to move to-and-fro in the said cylinder, one end of the saidcylinder being in pipe connection with the said running indicator andthe other'end bein open to atmosphere, a bypass from the closed end ofsaid cylinder to a port between the two outer portions of the saidtripartite piston, the middle portion of said pis-.

ton being adapted to control the port connecting the said portedcylinder with the said barring relay, and a cam operably connected totheiree piston assembly and adapted to move the said tripartite pistonagainst fluid pressure whereby a port in said ported cylinder is openedto apply an overriding pressure to the said barring relay piston to openthe said barring servo-motor cylinder and pressure operated vent-valveto exhaust.

7. A starting device as claimed in claim 1, wherein the said runningindicator comprises an oscillatory piston valve device arranged betweenthe said source of fluid pressure andthe said barring servo-motor andthesaid fluid pressure operated vent-valve, a link connection betweenthe said piston valve device and the free piston assembly adapted tooscillate the said piston valve in dependence on the reciprocation ofthe said free piston assembly, the said piston valve de- 12 vice beingadapted to establish the hydraulic connection with the said source ofpressurewhen at rest and to cut it off when oscillating.

8. A starting device as claimed in claim 1 in which the said startingrelay comprises a ported cylinder drained to exhaust at its inner endand adapted to be connected to the souce of fluid pressure at its outerend, a recessed piston valve adapted to move to-and-fro in the saidported cylinder, a spring adapted to bias the said piston valve towardsthe outer endof the said ported cylinder, the pipe connection controlledby the barring piston rod leading to a middle port of the said portedcylinder which is in communica tion with a recess of the saidpistonvalve in any position of said valve, a pipe connection with the saidmaster starting valve servo-motor of another port of the said portedcylinder adapted to be connected to exhaust in the outer p'ositionofthesaid piston valve and to be connected with the recess of the said pistonvalve in its inner position, a non-return valve arranged in the pipeconnection between the said ported cylinder and the said master startingvalve servo-motor adapted to open towards said servo-motor, a by-' passconnection shunting the said non-return valve, and an adjustableleak-off arranged in the said by-pass connection forming a time-lagdevice adapted to keep the said master starting valve open for a timesuflicient to enable a series of starting air impulses to be imparted tothe free piston assembly through the startin air timing valve afterfluid pressure from the'said running indicator is removed; v

9. A device as claimed in claim 8 comprising" an extension of the saidpiston valve extending to the outside of the said ported cylinderas ameans for manually moving the said piston valve into a position in whichit establishes fluid con nection between the said ports in the relaycylinder.

10. A starting device as claimed in claim 8 in which the said pistonvalve has two circular re-' cesses, the one nearer thedrained end of thesaid cylinder adapted to establish connection be tween the said ports,the other one nearer the closed end being connected by a bore with thedrained end of the said cylinder.

11. A starting device as claimed in claim 8 in which the said masterstarting valve servo-motor comprises two pistons, a compression springbetween the said pistons, the one of said pistons being adapted to beexposed to fluid pressure from the said starting relay and the otheroneof said pistons being adapted to lift the said master starting air valveoil? its seat under th action of th said spring.

ROBERT JAMES WELSH.

REFERENCES CITED The following references are of recordin the file ofthis patent:

UNITED STATES PATENTS 7

